First record of Hesperolabops nigriceps Reuter (Hemiptera: Miridae) on Opuntia ficus-indica in Milpa Alta, Mexico City

In recent years a species of Hesperolabops has become a problem as a pest of nopalitos, Opuntia ficus-indica, in Milpa Alta, in the south of Mexico City, which is the most important production region of this vegetable in the country. A survey of Hesperolabops in Milpa Alta has resulted in the first report of Hesperolabops nigriceps Reuter. This occurrence should be monitored and considered in future studies in order to avoid misidentification of Hesperolabops spp. Kirkaldy native populations there, and to avoid the confusion of the damage that may be caused on O. ficus-indica.     

The renowned cactus moth, Cactoblastis cactorum: its natural history and threat to native Opuntia floras in Mexico and the United States of America

Abstract. The cactus moth, Cactoblastis cactorum (Berg) (Phycitidae) is native to South America. It was released as a biological control agent against alien Opuntia- cacti in Australia in the 1920s, then in southern Africa, and latterly on several islands, including those in the Caribbean. In 1989, the cactus moth was discovered in Florida, in the United States of America, where it is now threatening the survival of indigenous Opuntia species. In this paper we identify some of the attributes that have contributed to the success of C. cactorum as a weed biological control agent. Many of these same qualities account for the problems that C. cactorum has caused in Florida and predispose it as a major threat to the speciose, native Opuntia- floras of Central and North America. An estimated 79 platyopuntia (prickly pear) species are at risk: 51 species endemic to Mexico; nine species endemic to the United States; and 19 species common to both countries. Many cultivated and wild Opuntia species, that are used in various ways, are also vulnerable to attack by C. cactorum , including at least 25 species in Mexico and three species in the United States, particularly the widely exploited and culturally important cultivars of O. ficus-indica . Some control strategies are suggested that may minimize the risk and consequences of invasion by the cactus moth. The wider implications of this threat to the practice of weed biological control and to conservation are discussed.     

Loss of water transport capacity due to xylem cavitation in roots of two CAM succulents

Loss of axial hydraulic conductance as a result of xylem cavitation was examined for roots of the Crassulacean acid metabolism (CAM) succulents Agave deserti and Opuntia ficus-indica. Vulnerability to cavitation was not correlated with either root size or vessel diameter. Agave deserti had a mean cavitation pressure of -0.93 ± 0.08 MPa by both an air-injection and a centrifugal method compared to -0.70 ± 0.02 MPa by the centrifugal method for O. ficus-indica, reflecting the greater tolerance of the former species to low water potentials in its native habitat. Substantial xylem cavitation would occur at a soil water potential of -0.25 MPa, resulting in a predicted 22% loss of conductance for A. deserti and 32% for O. ficus-indica. For an extended drought of 3 mo, further cavitation could cause a 69% loss of conductance for A. deserti and 62% for O. ficus-indica. A model of axial hydraulic flow based upon the cavitation response of these species predicted that water uptake rates are far below the maximum possible, owing to the high root water potentials of these desert succulents. Despite various shoot adaptations to aridity, roots of A. deserti and O. ficus-indica are highly vulnerable to cavitation, which partially limits water uptake in a wet soil but helps reduce water loss to a drying soil.     

Effect of polysaccharides from Opuntia ficus-indica (L.) cladodes on the healing of dermal wounds in the rat.

In traditional medicine extracts of polysaccharide-containing plants are widely employed for the treatment of skin and epithelium wounds and of mucous membrane irritation. The extracts of Opuntia ficus-indica cladodes are used in folk medicine for their antiulcer and wound-healing activities. The present study describes the wound-healing potential of two lyophilized polysaccharide extracts obtained from O. ficus-indica (L.) cladodes applied on large full-thickness wounds in the rat. When topically applied for 6 days, polysaccharides with a molecular weight (MW)>10(4)Da from O. ficus-indica cladodes induce a beneficial effect on cutaneous repair in this experimental model; in particular the topical application of O. ficus-indica extracts on skin lesions accelerates the reepithelization and remodelling phases, also by affecting cell-matrix interactions and by modulating laminin deposition. Furthermore, the wound-healing effect is more marked for polysaccharides with a MW ranging 10(4)-10(6)Da than for those with MW>10(6)Da, leading us to suppose that the fine structure of these polysaccharides and thus their particular hygroscopic, rheologic and viscoelastic properties may be essential for the wound-healing promoter activity observed.     

Rediscovery of Polypodium calirhiza (Polypodiaceae) in Mexico

This study addresses reported discrepancies regarding the occurrence of Polypodium calirhiza in Mexico. The original paper describing this taxon cited collections from Mexico, but the species was omitted from the recent Pteridophytes of Mexico. Originally treated as a tetraploid cytotype of P. californicum, P. calirhiza now is hypothesized to have arisen through hybridization between P. glycyrrhiza and P. californicum. The tetraploid can be difficult to distinguish from either of its putative parents, but especially so from P. californicum. Our analyses show that a combination of spore length and abaxial rachis scale morphology consistently distinguishes P. calirhiza from P. californicum, and we confirm that both species occur in Mexico. Although occasionally found growing together in the United States, the two species are strongly allopatric in Mexico: P. californicum is restricted to coastal regions of the Baja California peninsula and neighboring Pacific islands, whereas P. calirhiza grows at high elevations in central and southern Mexico. The occurrence of P. calirhiza in Oaxaca, Mexico, marks the southernmost extent of the P. vulgare complex in the Western Hemisphere.     

Exogenous Abscisic Acid Mimics Cold Acclimation for Cacti Differing in Freezing Tolerance

The responses to low temperature were determined for two species of cacti sensitive to freezing, Ferocactus viridescens and Opuntia ficus-indica, and a cold hardy species, Opuntia fragilis. Fourteen days after shifting the plants from day/night air temperatures of 30/20[deg]C to 10/0[deg]C, the chlorenchyma water content decreased only for O. fragilis. This temperature shift caused the freezing tolerance (measured by vital stain uptake) of chlorenchyma cells to be enhanced only by about 2.0[deg]C for F. viridescens and O. ficus-indica but by 14.6[deg]C for O. fragilis. Also, maintenance of high water content by injection of water into plants at 10/0[deg]C reversed the acclimation. The endogenous abscisic acid (ABA) concentration was below 0.4 pmol g-1 fresh weight at 30/20[deg]C, but after 14 d at 10/0[deg]C it increased to 84 pmol g-1 fresh weight for O. ficus-indica and to 49 pmol g-1 fresh weight for O. fragilis. Four days after plants were sprayed with 7.5 x 10-5 M ABA at 30/20[deg]C, freezing tolerance was enhanced by 0.5[deg]C for F. viridescens, 4.1[deg]C for O. ficus-indica, and 23.4[deg]C for O. fragilis. Moreover, the time course for the change in freezing tolerance over 14 d was similar for plants shifted to low temperatures as for plants treated with exogenous ABA at moderate temperatures. Decreases in plant water content and increases in ABA concentration may be important for low-temperature acclimation by cacti, especially O. fragilis, which is widely distributed in Canada and the United States.     

Evaluating hypotheses on the origin and diversification of the ringneck snake Diadophis punctatus (Colubridae: Dipsadinae)

Close affinities recognized between taxa in Mexico and the contiguous USA have led to a variety of biogeographical scenarios. One such hypothesis suggests that species that occur in both countries have an origin in central Mexico followed by dispersal into the USA. This study expands upon previous phylogeographical work of the ringneck snake Diadophis punctatus by incorporating new data from previously unsampled areas appropriate to critically assess hypotheses regarding a Mexican origin for this species. Maximum likelihood and maximum parsimony analyses inferred a derived position for the lineage from southern Mexico with constraint tests for alternate evolutionary hypotheses resulting in significantly worse likelihood values. Ancestral area reconstructions inferred an origin for D. punctatus in the south‐eastern USA followed by a south‐east to north‐east then westward directionality of historical migration. The position within the phylogeny and date estimate for the south‐western + Mexico clade suggests a recent invasion into central Mexico with expansion into the Nearctic/Neotropic transition zone. The extensive lineage diversity inferred from the mtDNA suggests that the genus is a complex of cryptic species whose conservational status should be re‐evaluated on both the national and regional levels. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 629–640.     

Molecular evolution of southern North American Cyprinidae (Actinopterygii), with the description of the new genus Tampichthys from central Mexico

Most of the recognized species of the genus Dionda inhabit drainages of the Gulf of Mexico from central Mexico to central Texas, USA, and have been considered a monophyletic group based on morphological, osteological, and allozyme investigations. Phylogenetic relationships of 15 species of Dionda and 34 species from closely related genera were inferred from one mitochondrial (cytb) and three nuclear gene sequences (S7, Rhodopsin, Rag1) totaling 4487 nucleotides. Separate analyses of all four genes yield congruent phylogenies; however the 15 putative species of Dionda evaluated were never recovered as a monophyletic group when species from nine related genera were included in the analyses. Among the ingroup taxa, one well-supported and highly divergent clade is consistently recognized and consists of six recognized and three undescribed northern species currently recognized in the genus Dionda. These nine species inhabit present or past tributaries of the Rio Grande basin of northern Mexico and southern USA, and were recovered as a basal clade in all analyses. Another large, also strongly supported clade, consisting of seven genera, include five southern recognized species currently in the genus Dionda, forming the sister group to the Codoma clade. These five species comprise the "Southern Dionda clade" and inhabit headwaters of the Pánuco-Tamesí drainage and some adjacent coastal rivers in the Tampico Embayment. The consistent and repeated identification of eight different clades recovered in most of the separate gene analyses strongly supports a division of the non-natural genus Dionda. A new genus, Tampichthys, is proposed for the clade of species endemic to east-central Mexico and formerly in Dionda. Tampichthys and the putative monotypic genus Codoma are more related to Mexican species of the genera Cyprinella and Notropis than to other species referred to Dionda sensu stricto.     

The historical biogeography of the southern group of the sucker genus Moxostoma (Teleostei: Catostomidae) and the colonization of central Mexico

The historical biogeography of the southern group of Moxostoma Rafinesque, 1820, a genus of Nearctic freshwater fishes belonging to the Catostomidae, along its entire distribution in North America was inferred to: (1) determine the biogeographical events responsible for its current pattern of diversity and distribution; (2) correlate the climatic and geologic history of the region with the biogeographical pattern observed; and (3) trace the colonization route into central Mexico and the western Pacific slope drainages. The sequences of mitochondrial cytochrome b and the third intron of the growth hormone were obtained for the members of the southern group and related species of the Catostomidae. Phylogenetic analyses and relaxed molecular clock analyses were performed to determine the relatedness of the species and to estimate divergence times. To uncover biogeographical patterns, a dispersal–extinction–cladogenesis (DEC) analysis was conducted. The phylogenetic analyses were consistent with the historical hydrographic scenario in the region. The divergence times show that the southern group evolved during the Pliocene–Pleistocene. The DEC analyses showed that vicariance and dispersal played an important role in the current distribution patterns of the lineages in central Mexico, and allow us to trace an independent route of colonization from the northern areas of North America into central Mexico.     

Biomechanics and anatomy of cladode junctions for two Opuntia (Cactaceae) species and their hybrid

Hybridization between the introduced arborescent Opuntia ficus-indica and the native shrubby O. littoralis has led to populations, referred to as O. "occidentalis," which form thickets that can dominate hillsides of chaparral and that can survive fires. Because the thickets apparently develop via vegetative reproduction, O. "occidentalis" was hypothesized to have a greater ability than its parent species to reproduce vegetatively due to weaker cladode junctions. Of the three taxa, the junctions for O. "occidentalis" had the least amount of wood, despite having cladode masses and junction cross-sectional areas similar to those of O. littoralis. The cladodes of O. "occidentalis" resisted deflection about their junctions the least and their junctions required the least amount of applied mass and the smallest bending moment to fail mechanically. The junction wood for all three taxa consisted mostly of parenchyma, with lesser amounts of cells with thickened secondary cell walls, indicating that some junction strength depended on hydrostatic pressure, especially for terminal junctions. Libriform fibers, which contribute to support and resist bending moments, were about 80% less frequent in the sub-subterminal junctions of O. "occidentalis" than in O. ficus-indica and O. littoralis. Vascular tracheids, which probably reduced shear among cells in the wood, were 90% less frequent in the terminal and sub-subterminal junction wood of O. "occidentalis" compared to O. littoralis. Thus wood characteristics can account for the weaker junctions of O. "occidentalis" compared to those of O. ficus-indica and O. littoralis, which apparently increases the ability of the hybrid to reproduce vegetatively.     

Water Relations and Low-Temperature Acclimation for Cactus Species Varying in Freezing Tolerance

Opuntia ficus-indica and Opuntia streptacantha are widely cultivated cacti that can tolerate temperatures no lower than -10[deg]C, whereas Opuntia humifusa, which is native to southern Canada and the eastern United States, can tolerate -24[deg]C. As day/night air temperatures were decreased from 30/20 to 10/0[deg]C, the osmotic pressure increased 0.10 MPa for O. ficus-indica and O. streptacantha but 0.38 MPa for O. humifusa. The increases in osmotic pressures were due mostly to the synthesis of fructose, glucose, and sucrose. In addition, O. humifusa produced a substantial amount of mannitol during exposure to low temperatures. Substantial accumulation of sugars and mannitol in cells of O. humifusa may help prevent intracellular freeze dehydration and ice formation as well as provide noncolligative protection to its membranes. Mucilage was slightly higher in all three species at the lower temperatures. Extracellular nucleation of ice occurred closer to the equilibrium freezing temperature for plants at 10/0[deg]C compared with 30/20[deg]C, which could make the cellular dehydration more gradual and, thus, less damaging. Results from nuclear magnetic resonance indicated a restricted mobility of intracellular water at the lower temperatures, especially for O. humifusa, which is consistent with its lower water content and higher levels of low molecular weight solutes.     

Traditional Knowledge and Useful Plant Richness in the Tehuacán–Cuicatlán Valley,Mexico

Traditional Knowledge and Useful Plant Richness in the Tehuacán–Cuicatlán Valley, Mexico. This study systematizes ethnobotanical information about the interactions between people and plants, ethnofloristic richness, the relative importance of useful species richness in relation to general species richness, and plant management in the Tehuacán–Cuicatlán Valley of central Mexico. The study recorded a total of 1,605 useful vascular plant species (61.2% of the total species richness of the regional vascular flora), this being the region with the highest absolute richness of useful plant species in Mexico. The null hypothesis that plant families with a higher number of useful species would be those having a higher general species richness was analyzed through residuals method. The plant families richest in useful species were Poaceae, Asteraceae, Cactaceae, Cyperaceae, Mimosaceae, and Solanaceae, most of which also have the highest general floristic richness. However, analyses of use categories did not generally corroborate our hypothesis. About 1,335 of the useful species are wild, more than 500 species are submitted to some type of management (62 species are tolerated, 34 protected, 50 enhanced, and 358 cultivated), but only a few have been studied to document their process of domestication. This information can be useful for developing regional strategies of sustainable management of plant resources.     

Association of Vibrio cholerae with plankton in coastal areas of Mexico

The El Niño event of 1997/1998 provided an opportunity to carry out a field experiment in which the relationship of sea surface temperature and the association of Vibrio cholerae with marine plankton could be assessed in Mexican coastal and estuarine areas. Plankton samples were collected from May 1997 through June 1999. Sites included the Mexican ports of Veracruz, Coatzacoalcos and Frontera in the Gulf of Mexico and Ensenada, Guaymas, Mazatlán, Manzanillo, Acapulco and Oaxaca in the Pacific Ocean. Sampling was also accomplished during two oceanographic cruises in the Yucatan channel of the Caribbean Sea. Bacteriological analyses for V. cholerae serogroups O1 and O139 were carried out. Also, the taxonomic structure of the plankton populations was determined. Vibrio cholerae O1 was detected only in Veracruz samples collected during April, May and June 1999, when La Niña climatic conditions prevailed. It is concluded that V. cholerae O1 in Mexico derives from its marine and estuarine origin and not from sewage contamination. The significant number of Acartia tonsa copepodites and V. cholerae copepodite-positive samples suggests a significant role of this copepod in the occurrence and distribution of V. cholerae in coastal areas of Mexico.     

A New Acanthocyclops Kiefer, 1927 (Copepoda: Cyclopoida) from Central Mexico with Comments on the Distributionof the Genus in Middle America

A new species of Acanthocyclops Kiefer is described from central Mexico. It differs from its congeners by a combination of characters including mainly: 11–13 antennular segments, a spine formula of 3444 and modified setae on legs 2–4. The presence of a compound distal antennular segment is aberrant within the Cyclopoida. The new species seems to be related to Nearctic forms of the vernalis –robustus clade. Ancestors of this lineage probably reached central Mexico as a result of glaciation events and the new species is a remain of stranded postglacial populations; some of these forms were succesful in colonizing tropical lands. A key for the identification of the species of Acanthocyclops recorded in Mexico is included. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Morphological and molecular data for a new species of <Emphasis Type="Italic">Pomphorhynchus</Emphasis> Monticelli, 1905 (Acanthocephala: Pomphorhynchidae) in the Mexican redhorse <Emphasis Type="Italic">Moxostoma austrinum</Emphasis> Bean (Cypriniformes: Catostomidae) in central Mexico

Pomphorhynchus purhepechus n. sp. is described from the intestine of the Mexican redhorse Moxostoma austrinum Bean (Catostomidae) in central Mexico. The new species can be distinguished from the other seven described species of Pomphorhynchus Monticelli, 1905 in the Americas by a subspherical proboscis and 14 longitudinal rows with 16–18 hooks each; the third and the fourth row of hooks are alternately longest. Sequences of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and the large subunit (LSU) rDNA (including the domains D2-D3) were used to corroborate the morphological distinction between the new species and Pomphorhynchus bulbocolli Linkins in Van Cleave, 1919, a species widely distributed in several freshwater fish species across Canada, USA, and Mexico. The genetic divergence estimated between the new species and the isolates of P. bulbocolli ranged between 13 and 14% for cox1, and between 0.6 and 0.8% for LSU. Maximum likelihood and Bayesian inference analyses of each dataset showed that the isolates of P. bulbocolli parasitising freshwater fishes from three families, the Catostomidae, Cyprinidae and Centrarchidae, represent a separate lineage, and that the acanthocephalans collected from two localities in central Mexico comprise an independent lineage. In addition, our analysis of the genetic variation of P. bulbocolli demonstrates that individuals of this acanthocephalan from different host species are conspecific. Finally, the distribution, host-association, and phylogenetic relationship of the new species, when placed in the context of the region’s geological history, suggest that both host and parasite underwent speciation after their ancestors became isolated in Central Mexico.     

Host-plant affinities of two biotypes of Dactylopius opuntiae (Homoptera: Dactylopiidae): enhanced prospects for biological control of Opuntia stricta (Cactaceae) in South Africa

1. Until recently, neither the phycitid moth Cactoblastis cactorum nor the cochineal insect Dactylopius opuntiae have been satisfactory biological control agents of Opuntia stricta in South Africa.
2. In marked contrast, both of these agents have kept O. stricta under biological control for many decades in Australia.
3. In an attempt to improve the situation in South Africa, a stock of D. opuntiae was obtained from O. stricta in Australia during 1996.
4. Host-specificity tests confirmed that the newly imported D. opuntiae from Australia is a different biotype to the one already established in South Africa.
5. The Australian ('stricta') biotype thrives on O. stricta but is unable to develop satisfactorily on O. ficus-indica , while the converse is true for the South African ('ficus') biotype, which thrives on O. ficus-indica but fares poorly on O. stricta .
6. The integrity of the host-plant specificity of the two biotypes of D. opuntiae has important implications for biological control of Cactaceae in South Africa, and has greatly enhanced prospects that O. stricta can be brought under biological control successfully.     

A new species of Oochoristica (Eucestoda: Cyclophyllidea) parasite of Ctenosaura pectinata (Reptilia: Iguanidae) from Oaxaca, Mexico

During January 2002, 3 specimens of an undescribed species of Oochoristica Lühe, 1898, were collected in Ctenosaura pectinata (Wiegmann, 1834) from Santa Mará Mixtequilla, Oaxaca, Mexico. Oochoristica leonregagnonae n. sp. differs from 71 of 82 species of the genus by its large number of testes (78-112 [95] vs. less than 65 per proglottid, respectively). In addition, the numerous ovarian lobes (31-79 [51]) possessed by the new species distinguish it from the other 10, with a maximum of 20 ovarian lobes. The new species differs from Oochoristica acapulcoensis Brooks, Pérez-Ponce de León and García-Prieto, 1999, which also infects C. pectinata in Mexico, by the presence of numerous staining granules throughout the parenchyma of the scolex in the latter species; likewise, testes in O. acapulcoensis reach and even overpass the excretory canals, whereas in the new species they are limited to the central region between these tubules.     

Cloud forest dynamics in the Mexican neotropics during the last 1300 years

Key questions for understanding the resilience and variability of Mexican Neotropical cloud forest assemblages in current and future climate change include: How have human disturbances and climate change affected the dynamics of the cloud forest assemblage? What are the predominant processes responsible for its present day composition and distribution? Are the current conservation strategies for the cloud forest in accordance with preserving its natural variability through time? In this study, the temporal dynamics of the cloud forest in west‐central Mexico over the last ～1300 years were reconstructed using palaeoecological techniques. These included analyses of fossil pollen, microfossil charcoal, and sediment geochemistry. Results indicated that a cloud forest assemblage has been the predominant vegetation type in this region over the last ～1300 years. During this time, however, there have been changes in the vegetation with an apparent expansion of cloud forest from ～832 to 620 cal years bp and a decline from 1200 to 832 cal years bp . Climate change (intervals of aridity) and human disturbances through anthropogenic burning appear to have been the main factors influencing the dynamics of this cloud forest. The spatial heterogeneity reported for high‐altitude forests in this region, in concert with high beta diversity, appears to be a manifestation of the high temporal variability in species composition for these forests. Greater turnover in cloud forest taxa occurred during intervals of increased humidity and is probably representative of a higher temporal competition for resources among the cloud forest taxa. The present results support the current protection scheme for cloud forests in west‐central Mexico where areas are kept in exclusion zones to avoid timber extraction, grazing, and agriculture; this will maintain diversity within these forests, even if there are only a few individuals per species, and enable the forests to retain some resilience to current and future climate change.